structs: add Names() api call. Closes #26

README.md

@@ -43,6 +43,10 @@ m := structs.Map(server)
 // => ["gopher", 123456, true]
 v := structs.Values(server)
 
+// Convert the names of a struct to a []string
+// (see "Names methods" for more info about fields)
+n := structs.Names(server)
+
 // Convert the values of a struct to a []*Field
 // (see "Field methods" for more info about fields)
 f := structs.Fields(server)
@@ -73,6 +77,7 @@ s := structs.New(server)
 m := s.Map()              // Get a map[string]interface{}
 v := s.Values()           // Get a []interface{}
 f := s.Fields()           // Get a []*Field
+n := s.Names()            // Get a []string
 f := s.Field(name)        // Get a *Field based on the given field name
 f, ok := s.FieldsOk(name) // Get a *Field based on the given field name
 n := s.Name()             // Get the struct name

structs.go

@@ -171,6 +171,25 @@ func (s *Struct) Fields() []*Field {
 	return getFields(s.value, s.TagName)
 }
 
+// Names returns a slice of field names. A struct tag with the content of "-"
+// ignores the checking of that particular field. Example:
+//
+//   // Field is ignored by this package.
+//   Field bool `structs:"-"`
+//
+// It panics if s's kind is not struct.
+func (s *Struct) Names() []string {
+	fields := getFields(s.value, s.TagName)
+
+	names := make([]string, len(fields))
+
+	for i, field := range fields {
+		names[i] = field.Name()
+	}
+
+	return names
+}
+
 func getFields(v reflect.Value, tagName string) []*Field {
 	if v.Kind() == reflect.Ptr {
 		v = v.Elem()
@@ -387,6 +406,12 @@ func Fields(s interface{}) []*Field {
 	return New(s).Fields()
 }
 
+// Names returns a slice of field names. For more info refer to Struct types
+// Names() method.  It panics if s's kind is not struct.
+func Names(s interface{}) []string {
+	return New(s).Names()
+}
+
 // IsZero returns true if all fields is equal to a zero value. For more info
 // refer to Struct types IsZero() method.  It panics if s's kind is not struct.
 func IsZero(s interface{}) bool {

structs_test.go

@@ -442,6 +442,39 @@ func TestValues_Anonymous(t *testing.T) {
 	}
 }
 
+func TestNames(t *testing.T) {
+	var T = struct {
+		A string
+		B int
+		C bool
+	}{
+		A: "a-value",
+		B: 2,
+		C: true,
+	}
+
+	s := Names(T)
+
+	if len(s) != 3 {
+		t.Errorf("Names should return a slice of len 3, got: %d", len(s))
+	}
+
+	inSlice := func(val string) bool {
+		for _, v := range s {
+			if reflect.DeepEqual(v, val) {
+				return true
+			}
+		}
+		return false
+	}
+
+	for _, val := range []string{"A", "B", "C"} {
+		if !inSlice(val) {
+			t.Errorf("Names should have the value %v", val)
+		}
+	}
+}
+
 func TestFields(t *testing.T) {
 	var T = struct {
 		A string